1. Field of the Invention
The present invention relates to fluid system valves. The invention concerns, more particularly, polymeric valves and methods for manufacturing the valves that limit, check, or otherwise direct fluid flow within a fluid system.
2. Description of Background Art
Modern articles of athletic footwear often include two primary elements, an upper and a sole structure. The upper comfortably secures the foot to the sole structure and may be formed of a combination of materials that are stitched or adhesively bonded together, including leather, thermoset foam, and textiles. The sole structure ordinarily includes multiple layers that are conventionally referred to as an insole, midsole, and outsole. The insole is a thin, padded member located adjacent to the foot that enhances the comfort of the footwear. The midsole forms the middle layer of the sole structure and often includes a resilient, foam material, such as polyurethane or ethylvinylacetate, that attenuates impact forces and absorbs energy when the footwear makes contact with the ground. The outsole is usually fashioned from a durable, wear resistant material and includes texturing to improve traction.
In addition to a foam material, midsoles may include a fluid system that relies upon valves to direct the flow of fluid within the system. Fluid systems may be used to achieve a variety of benefits including enhanced cushioning, improved fit, or ventilation of the upper. With respect to cushioning fluid systems, U.S. Pat. Nos. 5,558,395 and 5,937,462 to Huang disclose fluid systems that utilize ambient air to pressurize one or more bladders that are positioned within the midsole. One-directional valves, also referred to as check valves, permit air to enter a pump or inflation system but prevent, or check, fluid flow in the opposite direction. U.S. Pat. No. 4,446,634 to Johnson et al. and U.S. Pat. No. 5,794,361 to Sadler disclose self-contained fluid systems that include two bladders in fluid communication. The bladders are joined by conduits that include valves for directing fluid flow. With respect to ventilation, U.S. Pat. No. 6,085,444 to Cho discloses an article of ventilated footwear that includes a series of bladders and one-directional valves that draw outside air into the system and then discharge the air into the upper, thereby reducing or eliminating the presence of moisture in the area immediately surrounding the foot.
The fluid systems discussed above utilize a variety of valve types to direct fluid flow within the system. U.S. Pat. No. 5,144,708 to Pekar and U.S. Pat. No. 5,564,143 to Pekar et al. disclose one-directional valves formed of two polymer layers attached along opposite sides to form a channel between the layers. The valves are manufactured as a separate component and then incorporated into a fluid system. Manufacturing of the valves includes the use of a barrier material that prevents the valve layers from being bonded to each other when the valve is incorporated into a fluid system.